How to Grow and Care for Jack-in-the-Pulpit (Bog Onion)

This unusual woodland curiosity is very easy to grow

Jack in the Pulpit
KenWiedemann / Getty Images

Jack-in-the-pulpit (Arisaema triphyllum) is a great choice for native plant gardeners in the eastern U.S. looking for an unusual specimen that is easy to grow. It is a species that fascinates children and the young at heart, a plant easy to picture in a fairyland setting. The appeal of the plant lies in its unusual "flower," consisting of an inner spadix (Jack) containing the actual flowers, surrounded by a modified leaf structure that forms a hooded spathe (the pulpit) that surrounds the spadix. The actual flowers are not showy; it is the hooded spathe that you notice from a distance in spring, especially when it is striped and/or tinged with purple.

By fall, some mature plants will also offer a cluster of showy red berries that become more visible after the spathe withers away. The berries shine brightly and will add considerable luster to your shade garden late in the growing season.

Jack-in-the-pulpit is a slow-growing perennial that is usually planted from corm-like roots in the fall, or potted nursery plants in the spring. Be aware that this plant contains oxalate crystals and is very toxic to people and animals if consumed. Eating it can cause extreme pain and swelling of the mouth and digestive tract.

Botanical Name Arisaema triphyllum
Common Name Jack-in-the-pulpit, bog onion, lord-and-lady, wake robin
Plant Type Herbaceous perennial
Mature Size 1-2 ft. tall, with a similar spread
Sun Exposure Partial to full shade
Soil Type Moist, humusy
Soil pH Acidic
Bloom Time April to May
Flower Color Greenish-purple
Hardiness Zones 4a-9a (USDA)
Native Area Eastern North America
Toxicity Toxic to people and animals

Jack-in-the-Pulpit Care

Jack-in-the-pulpit needs shade, an adequate water supply, and nutrients. If these three elements are provided, the plant is largely carefree.

To plant, make a 6-inch hole in the ground in the fall and drop in the corm-like root, as you would do if you were planting a crocus. Once the plants have come up in spring and put on some size, shovel 2 to 3 inches of mulch around them to conserve moisture.

The three-part compound leaf of bog onion may remind you of poison ivy (Toxicodendron radicans). The leaf structure also resembles that of trillium which shares the same native habitat.

Light

Some shade is an absolute must for Jack-in-the-pulpit. The plant performs well even in deep shade. Avoid too much direct sunlight at all costs.

Soil

These wildflowers do not demand the superb drainage that many plants do, making them an option for boggy soils. The idea is to mimic the native habitat, which is damp, acidic areas of the forest that are rich in organic matter.

Water

Evenly moist soil is another must for growing Jack-in-the-pulpit.

Temperature and Humidity

Jack-in-the-pulpit is reliably hardy in zones 4a to 9a, provided it gets the damp, humid conditions it craves. Try to provide the moist, boggy environment that gives the plant one of its common names—bog onion. During the growing season, it likes moderate conditions that avoid temperature extremes.

Fertilizer

Fertilizing with compost is sufficient in most cases. But you can use an acidifying fertilizer if necessary to lower the pH of alkaline soils into the acidic range these plants favor.

Types of Jack-in-the-Pulpit

The various types of Jack-in-the-pulpit are usually regarded as subspecies of the same plant, although some experts view them as separate species. The differences are fairly minor and gardeners usually have little reason to be concerned about which type is being offered. Commercial growers often neglect to even specify the subspecies: Arisaema triphyllumsubs. pusillum, Arisaema triphyllum. subs. stewardsonii, or Arisaema triphyllum subs. quinatum.

In addition, there are several other species in the genus that may be sold commercially as Jack-in-the-Pulpit but are a different species from Asia commonly called cobra lilies.

  • 'Arisaema consanguineum' has purplish with light green stripes, ending in a long "tongue" that makes it look like a cobra's head. This plant is a native of the Himalayas.
  • 'Arisaema saxatile' has a long tongue, but in this case, the tongue is the spadix and the spathe is white. This plant is native to China.
  • 'Arisaema griffithii' offers an elaborate light-green veining pattern at the top. It is commonly known as Griffith's cobra lily. It is a native of the Himalayan region of India.

How to Propagate Jack-in-the-Pulpit

The quickest way to propagate new plants is by splitting off the cormlets that form alongside the parent roots. Here's how to do it:

  1. In the fall when the plants have just entered dormancy, dig up the entire root clump, using a shovel or trowel. (Wear gloves to avoid skin contact.)
  2. Break or cut off the offsets that have formed alongside the main corm or tuber.
  3. Immediately replant the pieces (as well as the parent corm) in humus-rich soil in a location with light shade.
  4. Water well, then cover the planted pieces with mulch for the winter.

How to Grow Jack-in-the-Pulpit From Seed

Jack-in-the-pulpit seeds need to be cold-stratified to germinate. This means keeping them damp in sphagnum moss, in a refrigerator, for at least 60 days. Then, sow them in a flat filled with soilless commercial potting mix and keep the flat in a cool, damp place. Germination should take two to three weeks. Continue growing seedlings in the flat for two years before transplanting them into individual pots or into the garden. Correct watering is critical, as too much water will cause the seedlings to rot, while too little will also kill them.

Started from seed, Jack-in-the-pulpit will require as much as five years before they reach flowering maturity.

Overwintering

Don't feel compelled to clean up fallen leaves and plant debris from the area where Jack-in-the-pulpit is growing. This decaying material is essential to providing the plant with the nutrients and soil moisture it needs. Jack-in-the-pulpit is perfectly hardy in its established range (zones 4a to 9a) and requires no protection against winter cold.

Common Pests & Plant Diseases

While not a destination for most pests and diseases, Jack-in-the-pulpit is a favorite for slugs. This is easily remedied by placing a small dish of beer in your garden and letting the slugs crawl in for a drink.

How to Get Jack-in-the-Pulpit to Bloom

Be patient. This plant may take as much as four or five years before it is mature enough to bloom. If mature plants refuse to flower, it may be for one of the following reasons:

  • Too much sun: These plants absolutely require shade. If they receive more than a few hours of daily sunlight, they will be reluctant to bloom at all.
  • Barren, dry soil: These plants like porous, rich, humusy soil such as is found in damp woodland settings. Dense clay or dry soil will prevent them from blooming.

Common Problems With Jack-in-the-Pulpit

Most problems with Jack-in-the-pulpit arise because gardeners have trouble providing it with the consistent moisture it needs. Dry conditions will quickly cause the plant to go dormant, often before the plant has a chance to flower. Make sure your Jack-in-the-pulpit plants are getting enough water and are properly mulched to maintain soil moisture. This is not a plant well-suited to dry shade—it wants a dampish environment, such as that found in low-lying, boggy areas of a rainy forest floor.

FAQ
  • How can I use this plant in the garden?

    Jack-in-the-pulpit looks good when surrounded by a mass of low-growing shady ground cover such as (Impatiens walleriana). When Jack-in-the-pulpit goes dormant and leaves a hole in your shade garden in mid-summer, this is a good time to plug in some impatiens to fill those vacant spaces. It also is a good plant for woodland gardens, planted with other native shade-lovers, such as bleeding heart, Solomon's seal, or wild ginger. They can also work well beneath shade-loving viburnum shrubs, provided you keep them well watered.

  • How long does Jack-in-the-pulpit live?

    In ideal conditions, Jack-in-the-pulpit will form small colonies and gradually spread to fill shady spaces. Once established, a colony can survive for many decades, but occasional division (every four or five years) will keep the plants vigorous.

  • What about wildlife?

    Browsing animals such as rabbits and deer seem to understand the toxic nature of Jack-in-the-pulpit and generally leave it alone. The red berries, however, are eaten by birds and the flowers will attract a variety of pollinators.

Article Sources
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  1. Arisaema triphyllum. North Carolina State Extension.

  2. Arisaema triphyllumFlora of North America

  3. Bird, Richard. Arisaema. The Propagation of Hardy Perennials. Batsford Publishing, 1994.